1. Technical Field of the Invention
This invention relates to semiconductor photo transceiver arrays with silicon circuitry permitting selectable routing of detectors to emitters, and to methods for routing and mapping data channels in opto-electronic semiconductor devices; and in particular to methods for routing, mapping, rerouting and re-mapping internal and optical inter-connections in multi-array semiconductor devices and systems.
2. Background Art
The technology associated with electronics has evolved extremely rapidly over the last 40 years. Computers and related peripheral equipment, satellite and communication systems are becoming ever more sophisticated and powerful. However, data transfer into and out of processors remains a gating capability. The combination of increased parallelism and optics is the focus of optical interconnect technology.
One approach to optical interconnect technology uses so-called flip-chip techniques where the advantages of silicon process technology are combined with the optical properties of III-V semiconductor materials. Results to date indicate that this combination will lead to orders of magnitude increases in data transfer rates. These successes suggest that there will be enormous benefits to resolving the remaining issues associated with this technology.
Prior art FIG. 1 shows an example of so-called flip-chip technology that has been developed to exploit the advantages of CMOS substrates for some aspects of data transfer, and the optical advantages of III-V semiconductors. In this technology, emitter-detector arrays are fabricated separately from a CMOS substrate. The emitter-detector arrays are then inverted, aligned with the CMOS substrates, and secured in place using solder balls or bumps to form electrical contacts with modest mechanical adhesion properties, and using epoxy to rigidly mount the emitter-detector array to the CMOS chip. In FIG. 1, for clarity only a single pair of fiber optic cables is shown.
The separate arrays of detectors and emitters are interconnected by some suitable light carrying media, such as bundles of fiber optic cables. The alignment between the ends the these bundles, or other media, and the arrays causes errors in mapping of the elements of one array with the elements of another array.
With whatever method one uses to connect one array of transmitters to an array of receivers, or one array of transceivers to another array of transceivers, alignment is an issue. In other words, what is needed is a way to determine that the arrays are aligned to produce a useful device.
Assembly processes are imperfect, so there will be some misalignment, even if the effect on the performance of the system is negligible. In a production environment the effect of small amounts of misalignment will decrease yield, which costs money in terms of lost revenue.
Prior art FIG. 2 shows a schematic representation of the effect of misalignment. The darker squares represent light from fibers coupled to the transceivers in a remote array, and the lighter squares represent the transceivers in the present array. In FIG. 2A there is some degradation of coupling, but a one-to-one correspondence between transceivers remains. However, in FIG. 2B, some of the light fibers overlap more than one transceiver, while others fail to overlap any transceivers. In general, the types of misalignment include rotation, linear displacement, scaling, and a combination of these three basic types of misalignment. What is needed is a way to increase the tolerance to slight misalignment of transceiver arrays when coupling arrays.
Connecting nodes requires the use of fiber bundles or some other point-to-point connection means. However, there will still be some amount of misalignment, which can cause system communication failures. What is needed is a way to increase the tolerance to slight misalignment of transceiver arrays when coupling nodes.
There would be only minimal utility to opto-electronic devices such as the ones shown in FIG. 1, if one array could be connected on only one other array. What is needed is a way to couple more than one array together.
If there is some misalignment between two transceivers, there will be an effect on other transceivers in other nodes. What is needed is a way to determine how the transceiver arrays are aligned in a ring or other network architecture so that channels can be assigned and correct data transfers between nodes in a network can occur.
In some applications, security of data transfer is critical. It is therefore very important to be able to ensure that data transfer is indeed secure. Therefore, what is needed is a way to increase the security with which data is transmitted from node to node.
Though small numbers of transceiver arrays consume modest amounts of power, large arrays consume copious quantities of power, and in so doing generate a lot of heat. Removing such large amounts of thermal energy is very challenging, but if the thermal load is not controlled the device may degrade prematurely. What is needed is a way to reduce the power consumed by a node.
Prior art that may provide useful context for the reader, includes the following:
U.S. Pat. No. 5,761,350, xe2x80x9cMethod and apparatus for providing a seamless electrical/optical multilayer micro-opto-electro-mechanical system assemblyxe2x80x9d, illustrates how opto-electronic interconnections can provide a practical solution to communications bottleneck problems when combining a multitude of information processing units to perform a function. As research activities progress in the field of serial or parallel board-to-board and module-to-module interconnections, some of the research focus has shifted to smaller physical dimensions, such as intra-module interconnections, which combines opto-electronic interconnections, multi-chip module packaging, and micro-electromechanical systems (MEMS) technologies at the module level. This disclosure presents integrated optical input/output (I/O) couplers on multi-chip modules (MCMs) using micro-machined silicon mirrors that are used with opto-electronic multi-chip modules (OE-MCMs). It uses microstructures that integrate optical wave guide networks, multi-layer electrical transmission line networks, micro-machined silicon mirrors, and C4-bonded photonic devices into a single structure. Using both sides of the silicon wafers, multiple metal layers and optical waveguide layers are fabricated for all types of metal or optical waveguide materials. The input/output coupling arrangement utilizes a combination of micro-machined silicon mirrors and through-holes across OE-MCM, integrated together into a single package.
U.S. Pat. No. 5,625,734, xe2x80x9cOpto-electronic interconnect device and method of makingxe2x80x9d, describes a waveguide having a core region and a cladding region. A portion of the cladding region forms a first surface and portions of both the core region and the cladding region form an end surface. There is an insulative flexible substrate having an electrically conductive tracing with a first portion and a second portion, wherein the first portion of the insulative flexible substrate is mounted on the end surface of the waveguide.
U.S. Pat. No. 5,428,704, xe2x80x9cOpto-electronic interface and method of makingxe2x80x9d, describes an interconnect substrate having a surface with electrical tracings. There is a photonic device with a working portion and a contact electrically coupled to one of the electrical tracings disposed oil the interconnect substrate. A molded optical portion encapsulates the photonic device, forming a surface. The surface passes light between the photonic device and an optical fiber. Alignment of the optical fiber is achieved by an alignment apparatus that is formed in the molded optical portion.
U.S. Pat. No. 5,420,954, xe2x80x9cParallel optical interconnectxe2x80x9d, describes an optical interconnect that couples multiple optical fibers to an array of opto-electronic devices. The interconnect includes a multiple optical fiber connector and an opto-electronic board. The multiple fiber connector can be mechanically attached to or detached from the board.
U.S. Pat. No. 5,857,042, xe2x80x9cOptical interconnection arrangementsxe2x80x9d, describes an optical interconnection arrangement consisting of a plurality of parallel optical interconnection channels. In each channel, there are an optical source, an optical receiver, a first lens and a second lens. The first lens conveys light from the source to the second lens, and the second lens refocuses the light at the receiver. Each source and the associated first lens are offset one relative to the other by a predetermined distance in a direction transverse to an optical axis of the first lens. The corresponding receiver and the associated second lens are offset one relative to the other by the same distance but in the opposite direction to the offset between the source and first lens. Each offset is equal and opposite to the corresponding offset in an adjacent channel. With such an arrangement, if a leakage portion of a light beam from the first lens in one channel impinges on the second lens in an adjacent channel, the leakage portion will be refocused at a position which is spaced from the receiver of the adjacent channel.
In one embodiment, in each channel, the first lens and the second lens share a common optical axis and the source and receiver are offset relative to their common optical axis. In an alternative embodiment, the source and the receiver share a common optical axis and the first lens and the second lens are offset relative to their common optical axis. Such optical interconnection arrangements are tolerant of translational or rotational misalignments between the sources and associated first lenses on the one hand and the receivers and associated second lenses on the other hand, which is of particular advantage for free space optical interconnects or couplers.
U.S. Pat. No. 5,748,818, xe2x80x9cMassive parallel optical interconnect systemxe2x80x9d, describes a massive parallel (MP) connector which includes a fiber optic connector having a polymer ferrule having multiple fibers mounted in V-grooves of the ferrule and beveled edges of the ferrule providing for alignment of the ferrule when the MP fiber optic connector is mated to a receptacle with an alignment assembly and an alignment member mounted within the alignment assembly to provide for precision alignment. A receptacle assembly has a first receptacle half for receiving a fiber optic connector of a first form factor and a second receptacle half for receiving a fiber optic connector of a second form factor.
U.S. Pat. No. 5,631,988, xe2x80x9cParallel optical interconnectxe2x80x9d, describes an optical interconnect that couples multiple optical fibers to an array of opto-electronic devices. The interconnect includes a multiple optical fiber connector and an opto-electronic board. The multiple fiber connector can be mechanically attached to or detached from the board. The optical interconnect consists of a multiple optical fiber connector with a holder with a first planar surface, a plurality of optical fibers attached to the holder, each fiber having a first end abutting the first surface so as to expose the first end for receiving or transmitting optical radiation. The first ends of the fibers form a fiber array having a first pattern. There is a guiding means disposed in the holder at predetermined positions with respect to the fiber array; and an opto-electronic board consisting of an opto-electronic device array monolithically formed on a semiconductor chip with the same pattern as the first pattern of the fiber array, with aligning means formed on the chip. The aligning means are disposed at substantially the same predetermined positions with respect to the array of opto-electronic devices as the positions of the guiding means relative to the fiber array, and the aligning means receives the guiding means so as to mechanically align the opto-electronic device array with the optical fiber array, whereby each opto-electronic device is aligned to an optical fiber, so that the opto-electronic device emits optical radiation into the fiber array or receives optical radiation from the fiber array.
The minimal device fundamental to the invention consists of a semiconductor photo-array on a silicon substrate with special enhancements. There is fabricated within the silicon circuitry in the substrate the capability to sense the signal strength received at each detector, and to make it available for interpretation in software for mapping of viable optical connections. The circuitry further provides for control through software for selectively switching and testing the routing or connections between detectors and emitters within a transceiver array or between the emitters and detectors of two, optically connected arrays. The circuitry may be enhanced, further extending the functionality and benefits of the invention, by incorporating software control inputs for adjusting the sensitivity or gain of each detector, and for selectively switching power off and on to each of the emitters and detectors.
For the purpose of this disclosure, terms other than xe2x80x9cmappingxe2x80x9d, such as configuring or switching, relate to the act of creating or altering all or part of a signal circuit path or channel. The term xe2x80x9cmapping,xe2x80x9d means generally to confirm what is the fully defined present set of connected points or links of each circuit path or channel of a single or multi-channel system. The term xe2x80x9cmapxe2x80x9d or xe2x80x9cmappingxe2x80x9d or xe2x80x9cre-mapxe2x80x9d or xe2x80x9cre-mapping,xe2x80x9d where the context admits, may include a reconfiguration or switching of one or more circuit paths within the system of interest, along with a new confirmation or mapping of what is the resulting new set of circuit paths or channels.
The methodology of the invention applicable to a single photo-transceiver array, facilitated by the software and circuitry described above, is the process of routing and rerouting the data transfer channels within a photo transceiver array to overcome device or system defects or failures and provide special operational flexibility, as will be better appreciated when the method is practiced at the next level of complexity.
The methodology of the invention, applied on a larger scale, provides for routing and mapping the data channels of a multi-array opto-electronic semiconductor device, including the intra-nodal connections and the inter-nodal connections that define each data channel or path through the device, for one or a multitude of purposes, including: adaptation to faulty, redundant, or missing connection paths resulting from lateral or rotational misalignment of arrays; isolation of defective emitters, detectors, and fiber optic strands; power and heat management; and time-based multiplexing of channel routing for security purposes.
The necessary software and silicon circuitry are initially employed to map a first order set of possible data channels between adjacent nodes and within nodes in the device, selecting out defective emitters, detectors or faulty fiber optic connections, and allocating from among the remaining possibilities a rule-based assignment of connection paths, forming a suitable operational channel set or map for data transfer. The rule may take into account any of several variables of interest in the specific application such as position, signal strength at the detector, plurality of detectors seeing a given emitter, non-useful emitters, architecture of the device or system, and the like.
The invention generally relies on a technique called over sampling, assuming there will be a surplus of detectors available for mapping of optical connections to accommodate misalignment of emitters to detectors and variable topologies, and for mapping and re-mapping of inter and intra-nodal connections for security, power management, and fault correction purposes.
It is an objective of the invention to provide a process for automatically configuring point-to-point connections between semiconductor photo arrays for increased alignment tolerance. It is a further objective to provide a process for automatically configuring point-to-point connections between the detectors and emitters of each semiconductor photo-transceiver array for better fault tolerance and security of data.
It is yet another objective to provide a way of operating such devices at less than maximum power consumption during routine operation, while providing for increased bandwidth during peak data-transfer demand times. It is also an objective of the invention to provide a process of automatically configuring data channel connections within the device or system so as to significantly increase fan out of an emitter signal to facilitate the mapping of star and ring topology devices, and such other complex topologies as may become useful in the development of such devices, for all the same advantages.
An additional objective of the invention is to provide for pixel re-mapping for increased reliability and security of data transmission, for re-routing if a fiber breaks, to improve the reliability and security of transmitted data, and for power reduction and bandwidth management across the global connection map.
Another additional objective is to provide for a useful distribution, such on a proximity-based or generally uniform distribution basis, when using a limited data channel set of emitter and detector allocations within the available array space, for more uniform power and heat distribution across the substrate. A still further objective is to provide means for allowing only the minimum amount of power needed to support the limited channel set, instead of powering connections that are not aligned usefully, or are not presently needed in the device topology. Another objective is to use smaller amounts of power during normal operations by turning some useful emitter-detector pairs off, but providing higher throughput during peak demand by turning all useful emitter-detector pairs on for short periods of time.
Other advantages and objectives will be apparent to those skilled in the art, based on the drawings, description of preferred embodiments, claims, and abstract that follow.